add shader backend + support for multiple shader formats

engine/shader_backend.odin

@@ -0,0 +1,52 @@
+package engine
+
+import "core:fmt"
+import "core:os"
+import sdl "vendor:sdl3"
+
+choose_shader_runtime :: proc(device: ^sdl.GPUDevice) -> (Shader_Runtime, bool) {
+	supported := sdl.GetGPUShaderFormats(device)
+
+	if .MSL in supported {
+		return {
+				backend = .Metal_MSL,
+				format = {.MSL},
+				shader_dir = "shaders/metal",
+				entrypoint = "main",
+			},
+			true
+
+	}
+	if .DXIL in supported {
+		return {
+				backend = .DSD12_DXIL,
+				format = {.DXIL},
+				shader_dir = "shaders/d3d12",
+				entrypoint = "main",
+			},
+			true
+
+	}
+	if .SPIRV in supported {
+		return {
+				backend = .Vulkan_SPIRV,
+				format = {.SPIRV},
+				shader_dir = "shaders/vulkan",
+				entrypoint = "main",
+			},
+			true
+	}
+
+	fmt.eprintfln("No supported shader format from device {got %v}", supported)
+	return {}, false
+}
+
+load_shader_blob :: proc(path: string) -> ([]u8, bool) {
+	data, err := os.read_entire_file(path, context.allocator)
+	if err != nil {
+		fmt.eprintfln("failed to read shader %s: %v", path, err)
+		return nil, false
+	}
+
+	return data, true
+}